Decision-making process could hold key to neurological disorders

Being forewarned is to be forearmed as the saying goes and the ability to anticipate events – from the completion of everyday tasks through to dealing with potentially life-threatening situations – means that better decisions can be made. Through some ground breaking discoveries of how exactly the human brain deals with uncertainty, a group of EU-funded researchers have helped to shed new light on the neural mechanisms underlying these behaviours.

Most promisingly of all, further research into how these mechanisms decline during healthy ageing could lead to important advances in how we treat pathological conditions such as Parkinson’s disease, depression and stroke. Around 1.2 million people in Europe have Parkinson’s, a progressive neurological condition that is predominantly characterised by problems with body movements. Although it is not fatal in itself, as it progresses it can lead to more serious situations such as falls, swallowing problems and difficulties thinking.

The key success of the four-year ACTSELECTCONTEXT project, which was completed in May 2016, has been to show how three important brain signalling chemicals affect the way that humans handle uncertainty. Noradrenaline regulates our estimates of how unstable the environment is, acetylcholine helps us adapt to changing environments and dopamine pushes us to act on our beliefs about uncertainty.

The project combined pharmacological interventions and novel computational models to determine how these three chemicals enable our brains to learn the changing relationships in our environment. This work provided the researchers with key insights into how we are able to flexibly and efficiently make decisions in response to changes around us; the team were able to assert for example that declining dopamine levels might explain some of the problems seen in Parkinson's disease.

Furthermore, little is known about the concerted interplay between brain regions in terms of effective connectivity, which is required for flexible behaviour. The ACTSELECTCONTEXT project was able to demonstrate that brain regions controlling our movements can be influenced by other brain regions that make computations about what is likely to happen (for example your tennis opponent’s next shot), or brain regions that decide which movement may be the most rewarding (for example whether to go to the kitchen and open a packet of biscuits).

However, this influence only occurs when our decisions actually require a movement, as opposed to abstract decisions that do not require actions. Furthermore, disruption of the communication between brain regions for decision making and those for movement control could lead to problems in turning our decisions into appropriate movements, as seen in Parkinson’s patients, the team concluded.

These discoveries were made possible thanks to the involvement of 128 healthy participants, who took part in reaction time tasks designed to test how they handled uncertainty. Participants were all given either a placebo or a drug to block noradrenaline, acetylcholine or dopamine before starting the task. They were then asked to respond to a series of symbols. Probability patterns were changed without warning, forcing participants to detect new patterns and adjust their responses accordingly. The research was published this month in the open-access journal ‘PLOS’.